The present invention relates to an apparatus and a method for processing an image signal in order to prevent a display device such as a plasma display panel (PDP) from being burned-in and an image display apparatus utilizing the same. More specifically, the present invention relates to an apparatus for processing an image signal, etc. that generates pixel data located at interpolation positions at least in a horizontal or vertical interpolation direction based on pixel data contained in the input image signal to thereby obtain an output image signal in which the number of pixels in this interpolation direction is converted, whereby an unpleasant visual feeling due to movement of an image for the purpose of prevention of burn-in on a screen may be mitigated by changing a phase of each of the interpolation positions uniformly across all the pixels in a change unit smaller than 360° each time a predetermined time elapses, an interval between the adjacent interpolation positions being set to 360°, for every period of time a display position of the image is shifted by as much as one pixel, the period of time pertaining to a case where the display position of the image due to the output image signal is shifted by as much as one pixel in the interpolation direction, thereby allowing a pixel position of each of the interpolation positions to be shifted in the interpolation direction by a distance shorter than a distance between the pixels.
Conventionally, a PDP, for example, is known as a flat display panel. This PDP comprises two glass substrates between which rare gas including neon as its main component is contained and a pair of discharge electrodes which are regularly arranged, wherein by utilizing ultraviolet light generated through a discharge emission phenomenon that occurs when a voltage is applied to minute discharge cells formed at intersections between these two electrodes, fluorescent substances for three primary color signals of red (R), green (G), and blue (B) are stimulated, thereby emitting light therefrom so that a color image may be obtained.
The PDPs are grouped into a DC type and an AC type in accordance with the structure and driving method thereof. The DC type PDP has the electrodes exposed into a discharge space and emits light only during a period of time when a voltage is applied on it. Additionally, it is provided with a memory function by use of a driving method referred to as “a pulse memory approach”, which utilizes such a phenomenon that excited particles generated by discharge will facilitate subsequent discharge. The AC type PDP has electrodes covered by a dielectric substance (glass layer) in such a configuration that this dielectric substance serves as a capacitor, so that light emission is stopped instantaneously. Since this pulsed emission is repeated, AC voltages with alternating polarities are applied to the electrodes. Further, it has an influence on the effective voltage within the cell, which phenomenon provides the memory function whether the charge accumulated on a surface of the dielectric substance by discharge stays or not.
An image display apparatus using this PDP has an advantage of having a high luminance, a wide view angle, and a high capacity ratio and, therefore, is widely available as a display device for a personal computer, etc. However, if a still image is displayed on this PDP for a long period of time, so-called burn-in on the screen occurs, thereby deteriorating the displayed image.
To solve this problem, if an image is a still image and is displayed for a certain period of time, customarily the display position of the image is moved to prevent the image from being burned-in on the screen (see Jpn. Pat. Appln. Laid Open Publication No. 2000-338947).
To prevent burn-in on the screen, in the above-described case of moving the position where the image is displayed, the image is moved in pixel units. Therefore, it has a problem that such movement of the image gives an unpleasant visual feeling to a viewer.